AT&T had a lock on the iPhone for four years. Verizon got it in 2011 and finally Sprint trailed on a deal with Apple to get the iconic smartphone in its lineup. Now analysts are saying T-Mobile, the underdog carrier in the U.S., may start selling the iPhone as soon as next week.

Scott Craig, an analyst at Merrill Lynch, released a note indicating that "speculation is heightening" around a Deutsche Telekom deal to begin offering the iPhone to T-Mobile's 33 million customers. T-Mobile has upgraded its network to HSPA+ in 10 major metropolitan areas, which could handle the high-speed data requirements of an iPhone. In fact, some 1.5 million T-Mobile customers already use unlocked iPhones in the U.S.

"While this would be incrementally positive" for Apple, quotes Craig as writing, "any financial impact would be limited." Craig estimated that a T-Mobile deal would add about 4 million iPhones to Apple's sales chart in 2013, 1 percent to Apple's top line revenue and 2 percent to Apple's bottom line.

The Unlocked Population

T-Mobile knows it's been seeing consumer churn over its iPhone deficit. If T-Mobile scores the iPhone it could be AT&T that bleeds customers.

"If T-Mobile gets the iPhone it would help them," said Mike Disabato, vice president of Network and Telecom at . "Keep in mind that people who want an iPhone and don't want to subscribe with AT&T have either gotten an unlocked phone, which is prohibitively expensive, or they jailbroke the phone and went over to T-Mobile."

If T-Mobile gets the iPhone, Disabato also expects AT&T would get barraged with customer requests to unlock their Apple devices so they can move over to T-Mobile. But, Disabato added, consumers should keep in mind that T-Mobile's 3G is slightly different from what AT&T uses. Unless Apple has done some trickery with the baseband chipsets, he told us, the experience may not be as smooth as some would hope.

"From a business perspective having the iPhone would definitely help T-Mobile," Disabato said. "It will hurt AT&T. There will be some churn in T-Mobile's direction because in many areas AT&T has rotten coverage and T-Mobile's is much better."

AT&T's Low Service Ranking

AT&T may indeed have something to worry about. AT&T scored 62 out of 100 in the annual Consumer Reports survey ranking wireless service carriers. That's the worst of the Big Four providers. T-Mobile ranked only slightly better at 64, but consumers tend to think the grass is greener on the other side.

"Of the four major U.S. national cell-phone standard service providers, Verizon Wireless led the pack, receiving favorable scores for voice and data service quality, and also for support attributes like staff knowledge and resolution of issues. Sprint, T-Mobile, and AT&T each received mostly middling to low marks, particularly for voice and text service quality," the Consumer Reports team said.

"AT&T was lowest-rated overall, but its 4G LTE network was rated the most favorably of any carrier. Its users reported the fewest problems with that higher-speed service, which most new smartphones now use."